JP2005311679A - Piezoelectric vibrating element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric vibrating element independently generating a sound pressure characteristic and a frequency characteristic required in the market, such as a wideband and flat sound characteristic, as a result of reduction of a peak and a dip in a frequency graph produced by a polygonal piezoelectric element having a circular shape and a circumscribed circle. <P>SOLUTION: By generating the piezoelectric vibrating element including the polygonal piezoelectric element having no circumscribed circle and a vibrating plate, the distance from the center point of the piezoelectric vibrating element to circumference comes to variety. As a result, a sound pressure difference of the peak and the dip in the frequency graph becomes small, and thus wideband and nearly flat frequency characteristics are obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a piezoelectric vibration element using a diaphragm and a piezoelectric element.

  Piezoelectric vibration elements with a piezoelectric element attached to a vibration plate such as a metal plate or resin are mounted on electronic devices and portable devices as materials for speakers, receivers, microphones, etc. instead of magnets due to their small size and light weight. The shape of the piezoelectric element used therein is almost a polygon having a circumscribed circle such as a circle or a rectangle.

However, in the case of a piezoelectric element having a conventional shape, the shape of the electrode may be changed to the shape of the piezoelectric element because the reproduction sound quality deteriorates and it is difficult to reproduce sound in a low frequency band (for example, see Patent Document 1). An invention has been made to improve acoustic characteristics by changing the shape of the diaphragm from the shape of the piezoelectric element and dividing it (see, for example, Patent Document 2).
Japanese Patent Application No. 8-019095 Japanese Patent Application No. 2001-016692

  However, in the prior art as described above, since the shape of the piezoelectric element itself is not different from the conventional one, the frequency characteristics of the piezoelectric element itself are not changed. That is, in the case of a circular piezoelectric element, since the arrival distance of vibration energy from the center point to the periphery inside the circle is a radius and the distance is constant, in the graph of frequency characteristics that appears as a composite of vibration energy, a certain constant The feature of having one peak in the frequency band appears. Therefore, when a circular piezoelectric element is used, it is used for an application where it is advantageous to have one peak with a large sound pressure, such as an alarm buzzer.

Also, in the case of polygonal piezoelectric elements with circumscribed circles such as rectangles, the distance from the center point to the periphery is not constant, so the vibration energy combined according to the difference in distance is more diverse than the circle, Since the distance from the center point to the peripheral edge is close to the radius of the circumscribed circle, sound pressure peaks and dips occur in several frequency bands even in the graph of frequency characteristics.

  From the above, in the case of a polygonal piezoelectric element having a circular shape and a circumscribed circle, one or a plurality of sound pressure peaks and dips occur, resulting in poor reproduction sound quality, particularly when used as a speaker. The required broadband and flat acoustic characteristics cannot be obtained.

  In addition, in order to improve sound quality as in the prior art, devising the shape of the peripheral part and the housing structure leads to new production problems such as yield and labor and cost.

  The present invention has been made in view of such circumstances, and reduces the peak and dip of the frequency graph generated from a polygonal piezoelectric element having a circular shape and a circumscribed circle. It is an object of the present invention to provide a piezoelectric vibration element that can generate sound pressure and frequency characteristics required in the market.

In the present invention, a piezoelectric element having the same shape is attached to a vibration plate having a shape that is a polygon that does not have a circumscribed circle, has at least two opposing corners, and the corners are connected by curves. The above-described problems are solved by providing the attached piezoelectric vibration element.

  The present invention provides a piezoelectric vibration element in which a piezoelectric element having the same shape is attached to a polygonal diaphragm having no circumscribed circle, thereby making it possible to compare the conventional piezoelectric element with a circular or circumscribed circle. There are many types of combined vibration energy caused by the difference in the distance between the center point and the periphery, and as a result, flat acoustic characteristics can be obtained over a wide band. In addition, since the above acoustic characteristics can be realized by the piezoelectric vibration element alone, it is not necessary to devise peripheral parts or a housing structure.

  The best mode for carrying out the invention is shown by comparing the case where a speaker using the piezoelectric vibration element of the present invention is manufactured and the acoustic characteristics thereof with the case of a speaker using a piezoelectric element having a conventional shape.

  FIG. 1 shows a speaker using a conventional piezoelectric element. A piezoelectric vibration element 5 in which a rectangular piezoelectric element 1 is bonded to a diaphragm 2 having the same shape and a larger area is bonded on a resin 3 with an adhesive. The outer edge of the resin 3 is fixed by a frame 4. At this time, the diaphragm 2 and the frame 4 have no contact.

In the speaker of FIG. 1, the positive and negative electrodes are respectively taken out from the piezoelectric vibration element 5 and connected to an amplifier and a sound source (the amplifier and the sound source are not shown). When an audio signal is input to the piezoelectric vibration element 5 through an amplifier and a sound source, the piezoelectric vibration element 5 vibrates to reproduce sound.

The graph of FIG. 2 shows the frequency characteristics when a voltage of 6 V is input to the piezoelectric vibration element 5 and the sound reproduced at a position 10 cm away from the microphone is measured. The vertical axis of the graph represents the sound pressure, and the upper limit is 95 dB and the lower limit is 55 dB with a reference value of 75 dB. The horizontal axis of the graph represents frequency, and the frequency band range is 20 Hz to 20 KHz. As can be seen from FIG. 2, the frequency characteristics of the speaker using the conventional rectangular piezoelectric element 1 have a plurality of large peaks and large dips, so that the reproduced sound quality is not uniform, and particularly the frequencies around 5 KHz and 10 KHz. Will be heard in a protruding manner.

Figure 3 is a speaker using a piezoelectric vibrating element of the present invention, the piezoelectric vibrating elements 5 pasted to the vibration plate 2 having the identical shape and a larger area of the piezoelectric element 1 of the polygon that does not have a circumscribed circle It is bonded onto the resin 3 and the outer edge of the resin 3 is fixed by a frame 4. At this time, the diaphragm 2 and the frame 4 have no contact.
FIG. 4 is a diagram in which only the piezoelectric vibration element 5 in FIG. 1 is extracted.

In the speaker of FIG. 3, similarly to the speaker of FIG. 1, the plus and minus electrodes are taken out from the piezoelectric vibration element 5 and connected to an amplifier and a sound source (the amplifier and the sound source are not shown). When an audio signal is input to the piezoelectric vibration element 5 through an amplifier and a sound source,
When 5 vibrates, sound is reproduced.

At this time, the graph of FIG. 5 shows frequency characteristics when a voltage of 6 V is input to the piezoelectric vibration element 5 of FIG. 3 and the sound reproduced at a position 10 cm away from the microphone is measured. The method of taking the numerical values on the vertical and horizontal axes of the graph is the same as that of the graph of FIG. As can be seen from FIG. 5, in the case of the speaker using the piezoelectric vibration element of the present invention, the difference in the sound pressure between the peak and the dip is smaller in the frequency band of 250 Hz or higher than in FIG. Overall, frequency characteristics close to flat with a wider band are obtained.

  As described above, by using the piezoelectric vibration element of the present invention, a frequency characteristic close to flat can be obtained in a wider band than the piezoelectric element of the conventional shape, because of the difference in distance from the center point of the piezoelectric element to the periphery. This is because the generated vibration energy is generated more in the piezoelectric vibration element of the present invention, so that the peak and dip of the frequency characteristic graph are corrected.

  In the example, an experiment was performed using an octagonal piezoelectric vibration element having no circumscribed circle as shown in FIG. 4. However, the present invention is not limited to this shape, and has at least two opposing corners such as a lemon shape. Since the distance from the center point to the periphery of the piezoelectric element varies even if it is a polygon that does not have a circumscribed circle with a curved line between the corners and the corners, it is flat with a broadband as shown in FIG. A frequency characteristic close to can be obtained.

FIG. 1 is a diagram of a speaker using a piezoelectric element having a conventional shape. FIG. 2 is a graph showing sound pressure and frequency characteristics obtained when the speaker of FIG. 1 is used. FIG. 3 is a diagram of a speaker using the piezoelectric vibration element of the present invention. FIG. 4 is a view showing one shape of the piezoelectric vibration element of the present invention. FIG. 5 is a graph showing sound pressure and frequency characteristics obtained when the speaker of FIG. 3 is used.

Explanation of symbols

1 Piezoelectric element 2 Diaphragm 3 Resin 4 Frame
5 Piezoelectric vibration element

Claims (2)

A piezoelectric vibration element in which a piezoelectric element is attached to one or both surfaces of a vibration plate, and the vibration plate has the same shape as the piezoelectric element and does not have a circumscribed circle having the same area as the piezoelectric element or an area larger than the piezoelectric element. A piezoelectric vibration element characterized by being a polygon. 2. The piezoelectric vibration element according to claim 1, wherein the piezoelectric vibration element has a shape having at least two opposing corners and connecting the corners with a curve.

Images